Conveyer tapes are the subject of an EIA Standard, identified as EIA-481 Revision A, published in 1986 by the Electronic Industries Association, Engineering Department, 2001 Eye Street NW, Washington, D.C. 2006, and entitled "Taping of Surface Mount Components for Automatic Placement," such publication being incorporated herein by reference and made a part hereof. The conveyer tapes disclosed in such Standard ("Standard 481") each comprises an underlying elongated flexible carrier belt or tape with sprocket holes therein, a stock of component parts disposed in a row thereof extending in the length of such belt, and an overlying plastic cover tape extending in the length of such row over such parts and bonded by adhesive on either side of the row to the underlying carrier belt so as to hold such parts in place until it is time to remove them from the conveyer. When that time comes (as when, say, the conveyer tape approaches a work station), the leading end of the overlying cover tape is pulled away from the underlying carrier belt to expose forward ones of the transported parts to access from above so as to permit such exposed parts to be removed from the conveyer means by, say, a vacuum pick and place device.
EIA Standard 481 specifies that the plastic cover tape should have a thickness which, at the maximum, is 0.1 millimeter and that the "top cover tape shall have a peel strength of 0.4.+-.0.3 newtons measured at 175.degree.-180.degree. with respect to the component carrier along the longitudinal axis of the carrier tape."
In the past, the cover tape has been pulled away from the carrier belt by rupturing the bond between the tape and the adhesive which secures the tape to the belt (in which case the adhesive remains on the belt) or, alternatively, by rupturing the bond between such adhesive and the belt (in which case the adhesive remains adhered to the tape). The strength, however, with which the adhesive is bonded to the tape and belt is a factor which can vary significantly in value even in the length of any one conveyer tape on either one or both of the adhered sides. One disadvantage arising from such variation is that the force needed to produce separation of the cover tape from the carrier may fluctuate substantially above and below the range of 0.4.+-.0.3 newtons prescribed by EIA Standard 481. A more serious disadvantage is that it is not unusual for the strength of bonding of the adhesive to the tape and belt to be so high at places along the conveyer tape as to exceed the breaking strength of the cover tape. When, however, that circumstance occurs, the cover tape will break at those places with the unfortunate result ensuing that uncovered components at the forward end of the carrier will likely be spilled off of the conveyer by the shock of the breaking of the tape. Moreover, the component supplying operations must be stopped in order to rethread the end of the broken cover tape in the pulling mechanism, therefor, and that downtime is expensive. Alternately, when the bond strength is too low, spillage of components can occur to disrupt the supplying operation with resultant expensive downtime.